Shot Direction Research Articles

Perception of Kinematic Characteristics of Tennis Strokes for Anticipating Stroke Type and Direction

The purpose of this study was to determine the sources of visual information used by highly skilled tennis players in anticipating their opponent's shots. In Experiment 1, motion analysis of the strokes showed that the relative motion between the racquet and forearm was different between the ground strokes and lobs, but there were no reliable kinematic differences when shot direction was varied. In Experiment 2, 12 skilled tennis players observed the opponent hitting strokes in a normal video or in a point-light display with different segments occluded. Players' anticipation accuracy was not degraded by the use of the point-light display. Occluding the racquet and forearm significantly reduced the participant's ability to determine the type of stroke produced.

Perception of Kinematic Characteristics of Tennis Strokes for Anticipating Stroke Type and Direction

The purpose of this study was to determine the sources of visual information used by highly skilled tennis players in anticipating their opponent's shots. In Experiment 1, motion analysis of the strokes showed that the relative motion between the racquet and forearm was different between the ground strokes and lobs, but there were no reliable kinematic differences when shot direction was varied. In Experiment 2, 12 skilled tennis players observed the opponent hitting strokes in a normal video or in a point-light display with different segments occluded. Players' anticipation accuracy was not degraded by the use of the point-light display. Occluding the racquet and forearm significantly reduced the participant's ability to determine the type of stroke produced.

Training Perceptual Skill by Orienting Visual Attention

A major element in expert sports performance, particularly racket-and-ball games, is excellent anticipatory skill. A prestudy combined the temporal and spatial occlusion paradigms to ascertain which key stimuli badminton players use for anticipating the direction of overhead shots. The main study then evaluated a program for training anticipatory skills; 200 video clips were employed to orient attention toward these key stimuli. Participants were 63 badminton novices, 20 national league players, and 21 local league players. A transparent red patch (exogenous orienting) was used to orient attention toward the trunk up to 160 ms before racket-shuttle contact; the arm, from 160 ms to 80 ms before contact; and the racket, from 80 ms before to actual contact. Results showed that badminton novices who trained with this program significantly improved their anticipatory skill between post- and retention test compared with controls. Whereas local league players improved from pre- to posttest, training had no effect on expert national league players. It is concluded that using red transparent patches to highlight the most informative cues in perceptual training programs is a promising way to improve anticipatory skill.

Improvement of Inner Surface for Machine Parts by Shot Peening

Shot peening process of inner surface of machine parts in which rebound shots collide with the inner surface was investigated. The jig used for rebound shot peening has the surface with a slope to the inner surface of machine parts, and the collision direction of shots was vertical to the inner surface. In this process, a compressed air type shot peening machine was employed. The influence of processing conditions was evaluated by the distributions of hardness, residual stress and surface roughness in the test pieces of pipes and coiled springs. The effect of shot peening increases with the increase of shots collision energy. A stress peening process for inner surface of coiled springs using rebound shots was also performed. The coiled spring was provided higher compressive residual stresses. The results of a fatigue test showed that the fatigue life of the spring was improved. The compressive residual stress reduces the tensile stress of coiled spring. It was found that the present process was suitable for improving the inner surface of machine parts.

Entrance, exit, and reentrance of one shot with a shotgun

The case being reported is one of a homicidal shotgun fatality with an unusual wound pattern. A 34-year-old man was shot at close range with a 12-gauge shotgun armed with No. 5 birdshot ammunition. The shot entered the left axillary region, exited through the left infraclavicular region, and thereafter penetrated the left side of the neck, causing tearing of the left common carotid artery and the right internal carotid artery. The entrance wound in the axilla was larger than the other wounds, and before autopsy it was believed that the shotgun had been fired twice, causing one wound in the neck and one wound perforating the infraclavicular region and exiting through the left axillary region. Thus, this case shows that unusual wound patterns in shotgun fatalities can easily lead to incorrect assumptions with regard to number and direction of shots fired unless thorough investigation is carried out postmortem. Language: en

The effects of increased shooting distance in the basketball jump shot

Three-dimensional video techniques (50 Hz) were used to obtain images of basketball jump shots from one of three distances--short range (group 1, n = 5); medium range (group 2, n = 5); long range (group 3, n = 5)--from the basket, as performed by members of the men's quarter-finalist teams at the games of the XVI Universiade in Sheffield in 1991. Fifteen sequences were digitized, beginning 20 frames prior to take-off to 10 frames after release. To facilitate analysis, the sequences were rotated about the ball position in the final frame so that the shot direction was parallel to one of the pre-defined orthogonal axes. Mean (+/- 1 S.D.) ball release speed was found to increase with distance from the basket (group 1 = 3.04 +/- 0.65 m s-1, group 2 = 4.71 +/- 0.74 m s-1, group 3 = 6.24 +/- 0.80 m s-1), while mean release angles were similar for all groups (group 1 = 48.8 +/- 10.1 degrees, group 2 = 47.8 +/- 5.8 degrees, group 3 = 51.9 +/- 5.5 degrees). The increased impulse necessary for the ball to reach the basket at increased shooting distances was derived from both an increase in angular velocity of the elbow joint of the shooting arm and an increased velocity of the centre of mass in the direction of the basket at release. Centre of mass speed at take-off was found to be influenced to a greater extent by the angular velocity of the ankle joint than that of the knee or hip joints.(ABSTRACT TRUNCATED AT 250 WORDS)

Computed tomographic classification of gunshot wounds of the head

Twenty-four patients following head bullet injuries were analyzed by CT. The major part, concerning 10 patients, refers to acute perforating lesions. Five cases showed penetrating injuries, 3 cases bolt injuries, the other ones lesions of the facial skull and residues of former bullet injuries. Because of a tempory cavitation the bullet track is wider than the bullet itself. The position of the skull fragments gives a hint to the shot direction. A reconstruction of intracranial bullet movements and spontaneous bullet dislocations is made possible by CT. It further shows secondary posttraumatic lesions.